Xanthine oxidase is an enzyme which plays an important role in in vivo uricogenesis. Thus, xanthine oxidase inhibitors are useful as remedies for hyperuricemia, which is a causal disease of gouty attack, and as preventive agents against gouty attack. Presently, allopurinol is the sole drug clinically used as a xanthine oxidase inhibitor. Compounds other than allopurinol having xanthine oxidase inhibitory activity have been reported, and some of them are under investigation for the development of pharmaceuticals (Japanese Patent Application Laid-Open (kokai) Nos. 5-310742 and 6-316578, and Japanese Patent Publication (kokoku) No. 6-41466).
Recently, purines have been reported to have pharmacological activities such as bronchodialating action, and therefore, use of the compounds as pharmaceuticals is expected [Pharmaceutical Society of Japan, Lecture Summaries of the 112th Annual Conference, 233 (1992)]. However, xanthine oxidase inhibitory activities of those compounds have so far not been reported.
Accordingly, the primary object of the present invention is to provide novel purine compounds endowed with xanthine oxidase inhibitory activity.